Amino Acid Mediated Intramolecular Asymmetric Aldol Reaction to Construct a New Chiral Bicyclic Enedione Containing a Seven-Membered Ring: Remarkable Inversion of Enantioselectivity Compared to the Six-Membered Ring Example

A detailed study to assess the enantioselectivity of the amino acid mediated intramolecular asymmetric aldol reaction of 1,3-cycloheptanedione bearing a C-2 methyl substituent has been undertaken. The cyclizations were mediated by a series of l-amino acids in the presence of an acid cocatalyst. Strikingly, the process is characterized by an inversion of enantioselectivity when compared to a similar reaction involving the 1,3-cyclohexanedione counterpart.